Thuc notes © 2021

CPU Register

Part of series computer architect |
  • It’s high-speed memory storage used by the processor.
  • It’s used support for the processor to store, decode and execute computer instruction.
  • It’s the fastest memory level in computer architect

Memory register types:

  • Accumulator (Arithmetic Logical Unit)
    • Performing arithmetic operations and also in logical operations
    • Holds the initial data, intermediate results and final result of the instruction
  • Flag Register
  • Memory Data Register
    • Store data to be written into or to be read out from the addressed location.
  • Program Counter
    • Is called “instruction pointer”.
    • Store address of next instructions need to fetch or execute.
  • Instruction Register
    • Store instruction that’s fetched from memory. Unit control will use it to decode and execute
  • Stack Control Register
  • Memory Buffer Register
  • Index register
  • Memory address register
    • Store address of memory unit

Fetch execute cycle:

  • Basic operation of a computer to fetch instruction from memory and execute them.
  • Steps:
    • PC (program counter) contains the address of the memory location that has the next instruction.
    • Memory’s address to copy to MAR (memory address register) through address BUS
    • Instruction content at memory’s address that’s stored in MAR is copied into MDR (memory data register)
    • Instruction content in MDR is copied to CIR (current instruction register) through data BUS
    • PC (Program counter) increase value to be ready for the next instructions
    • CPU decodes instruction content that’s stored in CIR
    • CPU executes the decoded instruction
    • CPU sends a signal to other components of the computer through control buses
    • Continue next instruction by repeating the cycle